Advances in wireless communication technology have contributed to wide spread deployment of wireless communication networks. Examples of such wireless communication networks may include Global System for Mobile Communication (GSM), Code Division Multiple Access (CDMA), and Wideband Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMAX), Long Term Evolution (LTE), and so forth. Antenna is a relatively important element in these wireless communications networks, particularly in base stations. An antenna assembly may include an antenna array coupled with one or more active components, which may include a power amplifier (PA), a low noise amplifier (LNA), and various filters and duplexers.
To generate the amount of power required for the antenna array to transmit the radio frequency (RF) signals over the designated coverage area, cavity filters that are relatively large in size may often be used in power amplifiers, making them ill-suited for out-door installations. As such, a typical wireless network base station may configure the active components, including the power amplifiers, as an indoor unit. A feedline, also known as a feed, sometimes more than 100 feet long, may be used to carry the energy generated by the power amplifiers, including the RF signals, to the antenna array.
The length of the feedlines may adversely affect the sensitivity and balance between the RF signals to be transmitted and the RF signals received. For example, in a base station antenna assembly with 6 active elements, the power amplifier may generate 20 watts of power. However, each active element may only have a power of transmission of 2 watts when taking into account of the internal transmission loss. In order to shorten the length of the feedline, some base stations may install all or part of the active components, including the amplifiers, as an outdoor unit, near the antenna array. A jumper wire may be used to couple the active components with the antenna array. However, this may not completely address the problem because there may still be significant signal loss attributable to the jumper wire.
Additionally, more and more directional antenna arrays are being replaced by tilt adjustable antenna arrays. Base stations may control and adjust the antenna tilt angle either mechanically or electrically. Mechanical tilt may refer to physically tilting the antenna structure to reach a desired beam angle. Electrical tilt may refer to tilting the direction of the signal by manipulating the phases of the signal, which may be accomplished by adjusting the length of the feedline leading to the active elements of the antenna array, typically through a motor. However, the resolution of tilt angle adjustment made by adjusting the length of the feedline, through a motor, may be relatively coarse, usually about 1 degree.
With large-scale application and deployment of wireless communication systems, cost control may become increasingly important. Often, the power amplifiers may contribute a relatively significant percentage to the total system cost due to the fact that the cost of the power amplifiers may increase exponentially with the increase of the transmission power. In addition, other components of the antenna assembly, such as dividers, combiners and duplexers, may also need to be designed to operate under the high power rating or with high power tolerance, which may also undesirably drive up the cost of the total system.